Humans are not the only species that laughs. Other great apes will also display a response during play which you can easily recognize as a laugh:

This means that laughter itself is pretty old...but what is it for? Some scientists hypothesize that it's for social interest (polite laughter and smiling are often observed when people are trying to be social). It could be that laughter makes the person watching you laugh feel better about you. OR it could be that laughter makes you, yourself, feel better.

But those are just results. The question is, HOW does this effect take place? What is the physical basis for laughter making us feel good?

Well, these scientists think it might have something to do with endorphins. And endorphins have something to do with PAIN.

Dunbar et al. "Social laughter is correlated with an elevated pain threshold" Proceedings of the Royal Society B, 2011.

Endorphins are opioid chemicals that you actually produce, in your own body, and which can help combat pain or facilitate feelings associated with reward. Unfortunately, they are limited to the central nervous system, and do not cross the blood-brain barrier. This means that it's hard to measure endogenous levels of endorphins in humans, as most humans object strenuously to a spinal tap in the name of science. But there's a solution to this. You see, endorphins, particularly beta-endorphin, regulate pain responses via a central mechanism. So you can measure the activity of beta-endorphins in humans indirectly, just by measuring their pain tolerance. It's not a perfect measure, but it gives you an idea. And it's at least better than a spinal tap. Those really don't lend themselves to studies of laughter and happiness.

So the authors of this study needed to elicit laughter. In order to do this, they had to make the study social. Think about it, you generally don't laugh too much when you're by yourself, even if you're watching something funny (unless, of course, you are practicing your Mad Scientist Laugh, which must be done at least once a day to really keep in practice). The easiest laughter and the most laughter is to be found in groups. So the authors tested various types of group laughter. They tested someone watching a serious or a funny video alone, and then watching a serious or funny video in groups (the serious video was a documentary, no word on what the comedy video was), and counted how many times people laughed. In order to get a larger social setting, they Edinburgh Fringe Festival and looked at people watching either comedy or drama shows there as well (science and art collide. Now THAT is a fun way to do science!). After each video or live theater performance, they needed to check for beta endorphin. The hypothesis was that if beta endorphins were elevated and made people feel good after laughing, these people would ALSO have an increased pain tolerance, as elevated levels of beta endorphin also increase pain tolerance.

"I'm glad you liked the comedy video! Now, come here. This will only hurt...um...a lot."

To measure pain, the authors used three different methods. The first and third are the ones I'm most (personally, sigh) familiar with. The first was a cold temperature cuff, which was cooled to -16 degrees Celsius. I've usually seen the cold pain tolerance test done in the old fashioned way, where you stick your hand in a big tub of ice water and hold it there as long as you can, but the net result is probably the same. They just test how long you can stand it. The second one was a similar test, only this time using a blood pressure cuff on maximum. The third was used at the Fringe festival, when you don't really have your apparatus with you. They just had people lean against a wall, sitting, until their legs got tired and they FELL OVER.

That's a wall sit, and you'll be familiar with that one if you have done various workouts, including Pilates and strength training. For each of these tests, they tested people before and after the comedy exposure, and looked for the difference between the two pain exposures (this is particularly important for the wall sit, just timing people once is no good, people used to these can do them for a loooooooong time).

What you can see above is an experiment where a person was tested either alone with a documentary, alone with a comedy, or in a group with a comedy. You can see that following the group/comedy experience, pain tolerance went up (more for males than females). Laughter was also significantly higher in all group conditions as compared to when participants watched videos alone. This pain difference persisted when people were tested at the fringe festival, with actors and audience showing increased pain tolerance following comedy as compared to drama (though laughs were not measured in this condition).

So it appears that laughter elevates pain thresholds. The authors hypothesize that laughter triggers release of endorphins like beta-endorphin, and elevates pain thresholds through this mechanism, though of course without measures of beta-endorphin you can’t REALLY be sure. These painkilling effects may also be pro-social, helping us to bond socially. But it occurs to me that these effects might be useful in the clinic, that comedy videos and things that make us laugh could be used to help people tolerate pain a little better (if it does indeed work this way).

I only wish we could get a brain probe in there! I also think it would be interesting to see if laughter changes things like dopamine (a neurotransmitter associated with the rewarding aspects of stimuli). It wouldn’t surprise me. You could maybe look at dopamine function using PET, and find reward associated brain areas using MRI, but it’s probably a no go to create a social group scene in an MRI machine, and keeping your head still while laughing is a pretty tall order! Of course, that’s just me, and wouldn’t account for the pain relieving aspects here.

So the next time you’re in a fun, relaxed and happy social situation, stick your hand in a bucket of ice water and see what you can stand. You might surprise yourself!

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

ABOUT THE AUTHOR(S)

Scicurious

Scicurious has a PhD in Physiology from a Southern institution. She has a Bachelor of Arts in Philosophy and a Bachelor of Science in Biology from another respected Southern institution. She is currently a post-doctoral researcher at a celebrated institution that is very fancy and somewhere else. Her professional interests are in neurophysiology and psychiatric disorders. She recently obtained her PhD and is pursuing her love of science and writing at the same time. She often blogs in the third person.
For more information about Scicurious and to view her recent award and activities, please see her CV ( http://scientopia.org/blogs/scicurious/a-scicurious-cv/)

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